To investigate the benefit induced by adding a small amount of bonded reinforcing steel into a fully unbonded prestressed concrete beam, two well-founded and straightforward approaches for predicting tendon stress are proposed. The primary approach utilizes a flexural analysis to calculate member deformation. The supplementary approach employs a truss model to consider the additional member deformation due to shear force. Both approaches use a simplified iterative method. With these two approaches, a systematic parametric study is conducted to investigate the effects of various factors. The results indicate that adding little bonded reinforcement does significantly increase the stress increment in unbonded tendons at ultimate state for one-point loading as expected. Moreover, a lower span-to-depth ratio, the use of high-strength concrete, and a smaller mechanical reinforcement ratio also raise the stress increment.

To investigate the benefit induced by adding a small amount of bonded reinforcing steel into a fully unbonded prestressed concrete beam, two well-founded and straightforward approaches for predicting tendon stress are proposed. The primary approach utilizes a flexural analysis to calculate member deformation. The supplementary approach employs a truss model to consider the additional member deformation due to shear force. Both approaches use a simplified iterative method. With these two approaches, a systematic parametric study is conducted to investigate the effects of various factors. The results indicate that adding little bonded reinforcement does significantly increase the stress increment in unbonded tendons at ultimate state for one-point loading as expected. Moreover, a lower span-to-depth ratio, the use of high-strength concrete, and a smaller mechanical reinforcement ratio also raise the stress increment.